Many attempts have been made to increase physical properties such as high temperature stiffness, mechanical strength and creep resistance of a crystalline propylene polymer by compounding a glass fiber to the propylene polymer.
These glass fiber reinforced propylene polymers (hereinafter sometimes abbreviated to "FRPP"), however, have several defects. For example, (1) a characteristic silver streak-like pattern is formed on injection molded articles, for example, and thus their appearance is not satisfactory, (2) molded articles are subject to warp due to orientation of the glass fiber and a difference in degree of shrinkage between the glass fiber and propylene polymer, and so forth, and (3) when a coloring material is compounded, the resulting polymer composition is inferior in mechanical strength, pelletizability, appearance, scratch resistance, warp of article, and so forth. Thus, conventional FRPP are limited in their application for the fabrication of wide variety of products, for example, in their use as interior or exterior parts for cars.
In order to overcome the above-described problems, various methods have been proposed. In connection with the problems (1) and (3) as described above, an attempt to increase flow properties has been made. However, there has not been obtained a satisfactory resin composition. Thus it has been forced to regulate the amount of the glass fiber to be added. For the problem (2), it has been proposed to utilize a plate-like filler and a rubber-like material (see, for example, Japanese Patent Application (OPI) Nos. 136736/76 and 8054/77 (the term "OPI" as used herein means a "published unexamined Japanese patent application")). Utilization of such fillers or materials, however, gives rise to problems such as a reduction of high temperature stiffness and an increase in density.